Скачать или смотреть The Correct Structure of a DTO Class in Java

Discover the key differences between using DTOs and regular objects in your Java classes, with practical examples and best practices for structured data transfer.
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Understanding DTOs: Which Structure is Correct?

When developing applications, especially those using frameworks like Spring, one concept that often arises is Data Transfer Objects (DTOs). Recent discussions have raised a critical question among developers: Should DTOs contain other DTOs, or should they contain normal objects? This guide aims to clarify this subject by comparing two examples of DTO classes, analyzing their structure, and providing insights into best practices.

The Scenario: Analyzing Two Example DTO Classes

Let's look at two different examples of a DTO class, both named TeamDTO.

First Example: Using DTOs

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Second Example: Using Entities

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The Key Question

The immediate question that arises is whether the attributes in a DTO class should be other DTOs or actual entity objects. The nested objects—are they helping or hindering?

The Correct Approach: Use DTOs Within DTOs

Explanation of Correctness

In the examples above, the first example, using MatchResponseDTO, is actually the preferred structure. Here’s why:

Encapsulation of Data: DTOs are meant to encapsulate data for transfer. If a DTO contains normal objects, especially entities, it compromises the objective of controlling and streamlining the data being passed around.

Avoiding Data Leakage: Entities often contain sensitive information (e.g., user passwords) or may incorporate complex relationships that can lead to inadvertent disclosures or circular references. DTOs provide a clean slate to structure and filter out the necessary fields.

Simplicity in Conversion: When dealing with complex entities that may have cyclical references (like a Match that has a reference to a List<Match>), using DTOs reduces the risk of errors during JSON (or other format) serialization.

Best Practices

To ensure your DTOs maintain their purpose, consider the following best practices:

Create Clear Boundaries: Maintain a distinct separation between DTOs and your persistent entities or models. This allows for independent changes in either layer without affecting the other.

Use DTOs for All Related Attributes: If your DTO has references to other classes (like DivisionDTO or MatchResponseDTO), ensure those classes are also DTOs themselves.

Refer to Design Patterns: For those interested in deeper theoretical aspects, exploring "Domain Driven Design" might provide valuable insights. However, be mindful that many of the concepts can be abstract and complex.

Conclusion

In conclusion, when designing your DTO classes, it’s essential to maintain a structure that consists exclusively of other DTOs rather than mixing them with regular entity objects. This not only ensures secure and effective data transfer but also adheres to software engineering best practices, promoting better design and maintainability.

Understanding the role of DTOs is a critical component for any developer working with data-oriented applications. By adhering to the correct structure, you can enhance the reliability and clarity of your applications.